An inexpensive biosensor is provided that can realize an electrochemical analysis and perform measurement with high accuracy or convenience. The biosensor is an immunological sensor that enables measurement anywhere at anytime by anyone while keeping convenience. The biosensor includes: an electrode sensor unit 4 in which an electric conductive layer 2 is provided on an electrode-unit forming substrate 1 having an insulating property and an electrode portion 3 for detecting an electrochemical signal is formed on the electrode-unit forming substrate 1; and a chromatographic sensor unit 10 in which an extended layer 7 including a porous film for extending a specimen solution is provided on an extended-portion forming substrate 6, wherein the electrode sensor unit 4 and the chromatographic sensor unit 10 are stacked with the extended-portion forming substrate 6 interposed between the electrode sensor unit 4 and the chromatographic sensor unit 10.